CN115305365B - Device and method for purifying rare earth metal by Czochralski method - Google Patents
Device and method for purifying rare earth metal by Czochralski method Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 101
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 101
- 238000000034 method Methods 0.000 title claims abstract description 41
- 239000013078 crystal Substances 0.000 claims abstract description 29
- 239000003870 refractory metal Substances 0.000 claims abstract description 29
- 229910052751 metal Inorganic materials 0.000 claims abstract description 27
- 239000002184 metal Substances 0.000 claims abstract description 27
- 238000002844 melting Methods 0.000 claims abstract description 22
- 230000008018 melting Effects 0.000 claims abstract description 22
- 239000007788 liquid Substances 0.000 claims abstract description 21
- 238000001816 cooling Methods 0.000 claims abstract description 13
- 238000004321 preservation Methods 0.000 claims abstract description 8
- 238000003723 Smelting Methods 0.000 claims abstract description 5
- 239000000843 powder Substances 0.000 claims description 16
- 238000002425 crystallisation Methods 0.000 claims description 14
- 230000008025 crystallization Effects 0.000 claims description 14
- 229910052684 Cerium Inorganic materials 0.000 claims description 7
- 229910052746 lanthanum Inorganic materials 0.000 claims description 7
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims description 7
- 230000001105 regulatory effect Effects 0.000 claims description 6
- 229910052721 tungsten Inorganic materials 0.000 claims description 6
- 229910052777 Praseodymium Inorganic materials 0.000 claims description 5
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 5
- PUDIUYLPXJFUGB-UHFFFAOYSA-N praseodymium atom Chemical compound [Pr] PUDIUYLPXJFUGB-UHFFFAOYSA-N 0.000 claims description 5
- 229910052727 yttrium Inorganic materials 0.000 claims description 5
- 229910052692 Dysprosium Inorganic materials 0.000 claims description 4
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 4
- 229910052779 Neodymium Inorganic materials 0.000 claims description 4
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 4
- 239000011733 molybdenum Substances 0.000 claims description 4
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims description 4
- 229910052715 tantalum Inorganic materials 0.000 claims description 4
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 4
- 239000010937 tungsten Substances 0.000 claims description 4
- 229910052691 Erbium Inorganic materials 0.000 claims description 3
- 229910052688 Gadolinium Inorganic materials 0.000 claims description 3
- 229910052689 Holmium Inorganic materials 0.000 claims description 3
- 229910052765 Lutetium Inorganic materials 0.000 claims description 3
- 229910052771 Terbium Inorganic materials 0.000 claims description 3
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims description 3
- UIWYJDYFSGRHKR-UHFFFAOYSA-N gadolinium atom Chemical compound [Gd] UIWYJDYFSGRHKR-UHFFFAOYSA-N 0.000 claims description 3
- KJZYNXUDTRRSPN-UHFFFAOYSA-N holmium atom Chemical compound [Ho] KJZYNXUDTRRSPN-UHFFFAOYSA-N 0.000 claims description 3
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 claims description 3
- 229910052706 scandium Inorganic materials 0.000 claims description 3
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 claims description 3
- GZCRRIHWUXGPOV-UHFFFAOYSA-N terbium atom Chemical compound [Tb] GZCRRIHWUXGPOV-UHFFFAOYSA-N 0.000 claims description 3
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract description 41
- 238000000746 purification Methods 0.000 abstract description 19
- 230000000694 effects Effects 0.000 abstract description 8
- 238000001179 sorption measurement Methods 0.000 abstract description 3
- 239000007787 solid Substances 0.000 description 9
- 230000001276 controlling effect Effects 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- 229920006395 saturated elastomer Polymers 0.000 description 7
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 238000007670 refining Methods 0.000 description 5
- 229910001338 liquidmetal Inorganic materials 0.000 description 4
- 238000004857 zone melting Methods 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010924 continuous production Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 2
- 229920005591 polysilicon Polymers 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 150000002843 nonmetals Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005292 vacuum distillation Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B59/00—Obtaining rare earth metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B9/00—General processes of refining or remelting of metals; Apparatus for electroslag or arc remelting of metals
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Metallurgy (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Organic Chemistry (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention relates to a device and a method for purifying rare earth metal by a pulling method, wherein the rare earth metal is heated to 200-600 ℃ above the melting point of the rare earth metal, the vacuum degree is maintained, and the temperature is kept for a period of time; adding refractory metal into the rare earth metal solution, cooling to 51-100 ℃ above the melting point of the rare earth metal, and stretching seed crystal under the liquid surface of the rare earth metal solution for heat preservation for a period of time; cooling to 0.1-50 deg.c over the smelting point of RE metal, and pulling seed crystal or RE metal container to crystallize. The invention realizes the step-by-step impurity removal of rare earth metals by controlling the temperature and the vacuum degree in the furnace; meanwhile, the activity of the impurities in the rare earth metal liquid is reduced by the directional adsorption of the refractory metals on the impurities, the purification effect is enhanced, and the 2N-level rare earth metal can be purified to more than 4N-level in one step.
Description
Technical Field
The invention relates to the technical field of metallurgy, in particular to a device and a method for purifying rare earth metals by a pulling method.
Background
The high-purity rare earth metal is a material base of high-performance rare earth magnetic, optical and electric functional materials, and is widely applied to national defense and military industry and strategic emerging industries such as new energy automobiles, integrated circuits, novel displays and the like.
Rare earth metals are active in nature and react easily with various metals, non-metals and gases, resulting in a large variety of impurities contained in rare earth metals, which can be classified into 4 types: class 1 is volatile impurities such as calcium, magnesium, fluoride, etc.; class 2 is medium saturated vapor pressure type impurities such as iron, copper, aluminum, silicon, etc.; class 3 is crucible impurities such as tungsten, molybdenum, tantalum, etc., which have high melting points and extremely low saturated vapor pressures; class 4 is a gaseous impurity such as oxygen, nitrogen, hydrogen, and the like.
Since each purification method has only a removal effect on certain impurities, the high-purity rare earth metals with the grade of more than 4N are required to be prepared by adopting various purification methods. For example, low saturated vapor pressure metal lanthanum and cerium are obtained by metal thermal reduction or molten salt electrolysis, crude metal with the purity of 99% is subjected to vacuum refining to remove volatile impurities, and then partial metal impurities are removed by zone melting or solid electromigration to remove partial metal impurities and gas impurities; the method comprises the steps of performing vacuum refining on crude metal with purity of 99% obtained by thermal reduction of metal to remove volatile impurities, removing low vapor pressure impurities and partial gas impurities by vacuum distillation, and finally removing metal impurities with similar saturated vapor pressure or solid electromigration by zone melting to deeply remove gas impurities.
The two types of rare earth metals are required to be purified by adopting a plurality of purification methods, volatile impurities are removed by adopting vacuum refining firstly, then partial metal impurities and gas impurities are removed by adopting zone melting and solid electromigration, the single-pass purification amount of zone melting and solid electromigration is only tens of grams to kilogram, the high-purity metal yield is low, the purification time is long, the purification efficiency of the two types of high-purity rare earth metals is low, the cost is high, and the high-purity rare earth metals cannot be applied to the high-new technical field in a large scale.
The Chinese patent ZL200910098370.2 discloses a purification method of solar grade polysilicon, which mainly comprises the following steps: (1) heating and melting silicon in a graphite crucible, evaporating impurities at 1500-2000 ℃ under the condition of 0-500 Pa, (2) controlling the temperature of the silicon to 1410-1500 ℃, preparing silicon crystals by seed crystal guidance, (3) heating to 1600-1850 ℃ when the silicon liquid in the graphite crucible is about to be exhausted, controlling the vacuum degree of the silicon surface to be 0-5 Pa, evaporating the impurities in the crucible, (4) reducing the temperature to be below 800 ℃, adding the next batch of raw materials, and then repeating the steps (1) - (4) for continuous production.
Chinese patent CN 200910045029.0 discloses a method for purifying high purity aluminum by ultrasonic wave, wherein inert protective gas is introduced into a heating furnace chamber, and then aluminum in a crucible is melted; heating the aluminum liquid to 660-750 ℃, extending the seed crystal below the liquid level of the aluminum melt, starting an ultrasonic generating device, controlling the temperature of the melt near a melting point by adopting water-cooled forced cooling at the other end of the seed crystal, and slowly lifting the seed crystal upwards or slowly downwards guiding a crucible containing the aluminum melt after crystallization starts, wherein the lifting speed and the crystallization speed are kept consistent; the ultrasonic power is controlled to be between 0.2kW and 10kW, the finally formed aluminum ingot is cylindrical, the solid phase purity is above 5N, impurity elements are uniformly distributed in the purified crystal, the crystal grains are uniform and fine, and the average crystal grain size is below 100 mu m.
For the 2 prior art, the Chinese patent ZL200910098370.2 is used for continuously producing polysilicon under the vacuum condition of 0-500 Pa, and the main steps comprise volatilizing and removing impurities, crystal growth, cooling and evaporating residual impurities and charging for continuous production, but the residual gas pressure in the furnace is higher in the whole purification process, so that burning loss and gas impurity pollution are caused to rare earth metals; chinese patent CN 200910045029.0 proposes pulling high purity Al under inert atmosphere, but this method cannot remove high saturated vapor pressure impurities in rare earth metals; the two techniques cannot be used for purifying 4N-grade high-purity rare earth metals.
Disclosure of Invention
Aiming at the problems that the existing rare earth metal purification method is low in efficiency and the large-scale purification methods in other fields cannot be used for rare earth purification, the invention provides a device and a purification method for purifying rare earth metal by a pulling method.
In order to achieve the aim, the invention provides a device for purifying rare earth metals by a pulling method, which comprises a furnace body, a crucible, a pulling device and a refractory metal powder feeding bin;
the temperature and pressure inside the furnace body can be adjusted;
The crucible is arranged in the furnace body and is used for accommodating rare earth metal liquid;
the lifting device extends from the outside to the inside of the furnace body and is used for lifting and crystallizing the rare earth metal liquid;
the refractory metal powder feeding bin is positioned outside the furnace body, and the refractory metal powder is fed into the crucible through the feeding passage.
Further, the furnace body is connected with a vacuum pump and is provided with an air charging hole, and the internal pressure is regulated through vacuumizing and air charging.
In another aspect, a method for purifying rare earth metals by the Czochralski method is provided, comprising:
(1) Rare earth metal is heated to 200-600 ℃ above the melting point of the rare earth metal, the vacuum degree is maintained, and the temperature is kept for a period of time;
(2) Adding refractory metal into the rare earth metal solution, cooling to 51-100 ℃ above the melting point of the rare earth metal, and stretching seed crystal under the liquid surface of the rare earth metal solution for heat preservation for a period of time;
(3) Cooling to 0.1-50 deg.c over the smelting point of RE metal, and pulling seed crystal or RE metal container to crystallize.
Further, the rare earth metal includes lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, dysprosium, holmium, erbium, lutetium, yttrium, or scandium.
Further, the refractory metal is one or more of tungsten, molybdenum and tantalum,
Further, the addition amount of the refractory metal is 1-30% of the rare earth metal.
Further, in the step (1), the vacuum degree is maintained to be the pressure of <10 -2 Pa, and the heat preservation time is 10-240 min.
Further, the heat preservation time in the step (2) is 5-30 min, and the vacuum environment with the pressure of <10 -2 Pa or the inert atmosphere environment with the pressure of > 10 2 Pa is maintained.
Further, in the step (3), the rotation speed of the seed crystal or the metal container is 0-10 rpm, and the crystallization speed is 1-30 cm/h.
Further, in the step (3), the crystallization pressure is <10 -2 Pa in a vacuum environment or an inert atmosphere ring with a pressure of > 10 2 Pa. Further, the purified rare earth metal is a round bar or a pipe.
The technical scheme of the invention has the following beneficial technical effects:
(1) The invention realizes the step-by-step impurity removal of rare earth metals by controlling the temperature and the vacuum degree in the furnace; meanwhile, the activity of the impurities in the rare earth metal liquid is reduced by the directional adsorption of the refractory metals on the impurities, the purification effect is enhanced, and the 2N-level rare earth metal can be purified to more than 4N-level in one step.
(2) The invention saves the vacuum refining and purifying time of low saturated vapor pressure metal lanthanum and cerium, and the vacuum refining and vacuum distilling and purifying time of medium saturated vapor pressure metal praseodymium, neodymium, dysprosium and the like, thereby improving the purifying efficiency.
(3) The single-furnace yield of the invention exceeds 20kg, and the invention can realize the preparation of high-purity rare earth metal bars and tubes and the purification, casting and molding integrated preparation of rare earth metals.
(4) According to the purification device, the refractory metal powder feeding bin and the operation end of the lifting device are arranged outside the furnace body, so that the operation is convenient, and the preparation efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of the apparatus for purifying rare earth metals;
Wherein 1 to a furnace body; 2-crucible; 3-molten metal; 4-bracket; 5-lifting device; 6-seed crystal; 7-vacuum pump; 8-air filling holes; 9-refractory metal powder feeding bin; 10-a charging bin valve;
fig. 2 is a flow chart of a purification process.
Detailed Description
The objects, technical solutions and advantages of the present invention will become more apparent by the following detailed description of the present invention with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention.
The invention provides a device for purifying rare earth metal by a pulling method, which comprises a furnace body 1, a crucible 2, a bracket 4, a pulling device 5, a vacuum pump 7 and a refractory metal powder feeding bin 9.
The crucible 2 is arranged in the furnace body 1 and is supported by the bracket 4, and the temperature in the crucible 2 is heated and regulated by the furnace body 1. The lower end of the lifting device 5 is provided with a seed crystal 6 which can move up and down, and the operating end is kept outside the furnace body 1.
The furnace body 1 is connected with a vacuum pump 7, and the furnace body 1 is vacuumized through the vacuum pump 7. The furnace body 1 is also provided with an air charging hole 8 for charging air into the furnace body 1 to adjust the pressure in the furnace body 1.
The refractory metal powder adding bin 9 and the feeding bin valve 10 are arranged outside the crucible 2, and after the feeding bin valve 10 is opened, the refractory metal powder adding bin 9 is connected to the crucible 2 through a feeding passage, so that the refractory metal powder is added outside the crucible 2 to the crucible 2.
The crucible 2 is internally provided with a molten metal 3, the pressure and the temperature are regulated, volatile impurities in rare earth metals are removed, the dynamic pressure is kept to be less than 10 -2 Pa, and generated volatile substances are pumped out by a vacuum pump 7. Adding refractory metal powder into a crucible, regulating the temperature and pressure in the crucible 2, regulating a pulling device 5, stretching a seed crystal 6 below the liquid level of liquid metal, reducing the temperature to be 0.1-50 ℃ above the melting point, slowly pulling the seed crystal upwards or slowly downwards pulling the crucible containing rare earth metal liquid after crystallization starts, controlling the crystallization speed to be 1-30 cm/h, and finally forming the round bar or pipe with the purity of solid rare earth metal above 4N.
In another aspect, a method for purifying rare earth metals by a Czochralski method is provided, comprising the steps of:
(1) Adding rare earth metal into a crucible of a pulling furnace, vacuumizing, heating to 200-600 ℃ above the melting point of the rare earth metal under the condition that the dynamic pressure is less than 10 -2 Pa, and preserving the temperature for 10-240 min to remove volatile impurities in the rare earth metal.
(2) Adding refractory metal powder into the crucible, cooling to 51-100 ℃ above the melting point of rare earth metal in a vacuum environment with the pressure of less than 10 -2 Pa or an inert atmosphere environment with the pressure of more than 10 2 Pa, and extending seed crystal into the liquid metal to keep the temperature for 5-30 min.
(3) The temperature is reduced to 0.1-50 ℃ above the melting point under the vacuum environment with the pressure of <10 -2 Pa or the inert atmosphere with the pressure of more than 10 2 Pa, the seed crystal is slowly lifted upwards or the crucible containing rare earth metal liquid is slowly pulled downwards after crystallization starts, the rotation speed of the seed crystal or the crucible containing rare earth metal liquid is controlled to be 0-10 rpm, the crystallization speed is controlled to be 1-30 cm/h, and finally the round bar or the pipe with the solid rare earth metal purity of more than 4N is formed.
Further, rare earth metals include lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, dysprosium, holmium, erbium, lutetium, yttrium, or scandium.
Further, one or more of refractory metals tungsten, molybdenum and tantalum, wherein the addition amount of the refractory metals is 1-30% of rare earth metals.
Example 1
Adding 30kg of rare earth lanthanum with purity of 99% into a crucible of a pulling furnace, vacuumizing, heating to 580 ℃ above the melting point of the rare earth under the dynamic pressure of 10 - 5 Pa, and preserving heat for 200min to remove volatile impurities in the rare earth; adding 9kg of refractory metal powder into the crucible, cooling to 100 ℃ above the melting point of rare earth metal under the vacuum condition of 1X 10 -5 Pa, and stretching seed crystal with the diameter of 1cm into the liquid level of liquid metal for heat preservation for 20min; and (3) reducing the temperature to 30 ℃ above the melting point under the condition of 1X 10 -5 Pa, lifting the seed crystal upwards at the rotation speed of 2rmp and the crystallization speed of 25cm/h after the crystallization starts or slowly downwards guiding the crucible containing the rare earth metal liquid for 20min, controlling the rotation speed to be 6rmp, the crystallization speed to be 25cm/h and lifting for 3h, wherein the total amount of impurities such as Ce, pr, nd, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, Y, fe, si, al, ni, ca, mg, W, mo, ta and the like is 80-100ppm, and finally forming the solid rare earth metal round bar with the purity of 4N-4N 2.
Comparative example 1
97G of rare earth lanthanum with the purity of 99% is made into a round bar with the diameter of 10mm and the metal length of 20cm, the moving speed of a melting zone is 10cm/h under the condition of the vacuum degree of 5 multiplied by 10 -5 Pa, the smelting times are 15 times, the total amount of impurities such as Ce, pr, nd, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, Y, fe, si, al, ni, ca, mg, W, mo, ta is 200-400ppm, and finally the solid round bar with the purity of 3N6-3N8 is formed.
Example 2
Adding 30kg of rare earth praseodymium with the purity of 99% into a crucible of a pulling furnace, vacuumizing, heating to 580 ℃ above the melting point of the rare earth under the dynamic pressure of 10 - 5 Pa, and preserving heat for 180min to remove volatile impurities in the rare earth; adding 6kg of refractory metal powder into the crucible, cooling to 80 ℃ above the melting point of rare earth metal under the vacuum condition of 1X 10 -5 Pa, and extending seed crystals with the inner diameter of 10cm and the appearance of 12cm into the liquid metal liquid surface for heat preservation for 20min; and (3) reducing the temperature to 30 ℃ above the melting point under the condition of 1X 10 -5 Pa, controlling the rotating speed to be 8rmp and the crystallization speed to be 20cm/h, and pulling for 6h to finally form the metal pipe with the purity of 4N-4N3 of the solid rare earth metal.
Examples 3-12 referring to Table 1, it can be seen that the rare earth purity after purification reaches over 4N grade with less impurity content.
TABLE 1
In summary, the invention relates to a device and a method for purifying rare earth metal by a pulling method, wherein the rare earth metal is heated to 200-600 ℃ above the melting point of the rare earth metal, the vacuum degree is maintained, and the temperature is kept for a period of time; adding refractory metal into the rare earth metal solution, cooling to 51-100 ℃ above the melting point of the rare earth metal, and stretching seed crystal under the liquid surface of the rare earth metal solution for heat preservation for a period of time; cooling to 0.1-50 deg.c over the smelting point of RE metal, and pulling seed crystal or RE metal container to crystallize. The invention realizes the step-by-step impurity removal of rare earth metals by controlling the temperature and the vacuum degree in the furnace; meanwhile, the activity of the impurities in the rare earth metal liquid is reduced by the directional adsorption of the refractory metals on the impurities, the purification effect is enhanced, and the 2N-level rare earth metal can be purified to more than 4N-level in one step.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explanation of the principles of the present invention and are in no way limiting of the invention. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the scope and boundary of the appended claims, or equivalents of such scope and boundary.
Claims (8)
1. The method for purifying the rare earth metal by the pulling method is characterized in that a device for purifying the rare earth metal based on the pulling method is used for purifying the rare earth metal and comprises a furnace body, a crucible, a pulling device and a refractory metal powder feeding bin; the temperature and pressure inside the furnace body can be adjusted; the crucible is arranged in the furnace body and is used for accommodating rare earth metal liquid; the lifting device extends from the outside to the inside of the furnace body and is used for lifting and crystallizing the rare earth metal liquid; the refractory metal powder feeding bin is positioned outside the furnace body, and the refractory metal powder is fed into the crucible through the feeding passage; the furnace body is connected with a vacuum pump and is provided with an air charging hole, and the internal pressure is regulated through vacuumizing and air charging;
The method for purifying rare earth metal by a pulling method comprises the following steps:
(1) Rare earth metal is heated to 200-600 ℃ above the melting point of the rare earth metal, the vacuum degree is maintained, and the temperature is kept for a period of time;
(2) Adding refractory metal into the rare earth metal solution, cooling to 51-100 ℃ above the melting point of the rare earth metal, and stretching seed crystal under the liquid surface of the rare earth metal solution for heat preservation for a period of time;
(3) Cooling to 0.1-50 deg.c over the smelting point of RE metal, and pulling seed crystal or RE metal container to crystallize.
2. The method of purifying a rare earth metal according to claim 1, wherein the rare earth metal comprises lanthanum, cerium, praseodymium, neodymium, gadolinium, terbium, dysprosium, holmium, erbium, lutetium, yttrium, or scandium.
3. The method for purifying rare earth metals according to claim 1 or 2, wherein the refractory metal is one or more of tungsten, molybdenum, tantalum.
4. A method of purifying a rare earth metal according to claim 3, wherein the refractory metal is added in an amount of 1 to 30% of the rare earth metal.
5. The method for purifying a rare earth metal according to claim 1 or 2, wherein in the step (1), the vacuum degree is maintained at a pressure of <10 -2 Pa and the holding time is 10 to 240 minutes.
6. The method for purifying rare earth metal according to claim 1 or 2, wherein the holding time in step (2) is 5min to 30min, the vacuum atmosphere of the pressure <10 -2 Pa, or the inert atmosphere of the pressure > 10 2 Pa.
7. The method for purifying rare earth metal according to claim 1 or 2, wherein the rotation speed of the seed crystal or the metal container is 0 to 10rpm and the crystallization speed is 1 to 30cm/h in the step (3).
8. The method for purifying a rare earth metal according to claim 1 or 2, wherein the crystallization pressure in the step (3) is <10 -2 Pa in a vacuum atmosphere or > 10 2 Pa in an inert atmosphere, and further wherein the purified rare earth metal is a round bar or a tube.
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